This invention relates generally to high resolution pressure-sensing devices, and more particularly to such devices having an insulating flexible matrix loaded with filler particles.
It is known within the art that the resistance of an insulating matrix loaded with conductive particles decreases as the volume of conductive particles relative to the volume of the matrix increases. For example, as reported in Shaul M. Aharoni, xe2x80x9cElectrical Resistivity of a Composite of Conducting Particles in an Insulating Matrix,xe2x80x9d 43 Journal of Applied Physics 2463 (1972), which is hereby incorporated by reference, when the volume percent of conductive particles (defined as the volume of the conductive particles as a percentage of the volume of the matrix) for one particular composition is between approximately ten and twenty percent, the resistivity of the insulating matrix decreases substantially logarithmically. The Aharoni reference describes an experiment in which samples of a polymeric material are prepared such that each is loaded with a different amount of a metal material. The resistance of each material is then measured to ultimately derive the observed relationship between volume percent of conductive particles and resistance of the insulating matrix.
This phenomenon has subsequently been observed in other environments, as is shown by the research reported in Li Li and James E. Morris, xe2x80x9cElectrical Conduction Models for Isotropically Conductive Adhesive Joints,xe2x80x9d IEEE Transactions on Components, Packaging, and Manufacturing Technology, Part A, Volume 20, Number Mar. 1, 1997. However, it is not believed that the observed relationship has been put to useful technological applications. A significant limitation in doing so is the manner in which the Aharoni experiment is conducted. Each different sample of polymeric material, once loaded with conductive filler particles, yields an unchanging and nondynamic resistivity. Although interesting from a purely scientific standpoint to derive the observed relationship between volume percent of conductive particles and resistance of the polymeric material, this permanence in resistivity makes the phenomenon less than practical for useful applications. This may be a reason why useful innovations relying on the phenomenon is believed to not abundantly exist.
The above-described shortcomings are addressed by the present invention, which will be understood by reading and studying the following specification. The invention describes a pressure-sensing device having an insulating flexible matrix into which a plurality of filler particles are loaded. The matrix is flexible, so that its volume decreases as a force applied to the matrix increases. The volume ratio of the filler particles relative to the matrix therefore increases as the applied force increases. This results in the resistance of the matrix decreasing as the applied force increases, according to a preferred embodiment.
The novel pressure-sensing device is not limited by its potential applications. Embodiments described herein include a high-resolution pattern recognition device, and a pressure-sensitive cold-cathode display (CCD). Still other and further aspects, embodiments and advantages of the present invention will become apparent by reference to the accompanying drawings and by reading the following detailed description.